1. Field of the Invention
The present invention relates to a pickling tank for products such as metal band or strip. More specifically, the present invention relates to a substantially plastic pickling tank containing expandable seals allowing for thermal expansion of the trough section of the pickling tank.
2. Background Information
A large variety of pickling apparatuses have been devised for pickling sheet material such as carbon and stainless steel strip. Examples of these devices can be found in U.S. Pat. Nos. 2,650,599; 3,625,232; 4,950,333; 5,116,447; 5,248,372 and 5,412,966. Additionally, a wide variety of shallow bath pickling or turbulent bath pickling devices have been developed. As the name implies, the shallow bath pickling apparatuses are not as deep as conventional pickling baths and generally have a plurality of spray nozzles pumping pickling acid over the work product. The shallow bath pickling devices generally require a pickling acid supply system as well as a pickling acid recirculation system. The constant movement of the acid on the strip within the shallow bath pickling device provides a mechanical scrubbing action to help remove the scale off the workpiece. Additionally, the pickling acid is more homogeneous throughout a shallow pickling bath. However, a shallow bath pickling device must pump a significant amount of pickling acid through the bath. Samples of shallow bath pickling devices can be found in U.S. Pat. Nos. 4,807,653; 4,996,998 and 5,282,485.
As described in U.S. Pat. No. 4,901,744, pickling bath tanks have historically been made out of metal or granite which have significant drawbacks in cost, weight and lack of corrosion resistance of the resulting pickling tank. Additionally, due to elevated operating temperatures, the tanks undergo thermal expansion during use. Corrosion-resistant plastic tanks will expand to a greater degree than metal or granite tanks. The prior art patents do not significantly provide for expansion joints allowing for expansion of the troughs while preventing the escape of pickling acid. Any large amount of tank expansion can detrimentally affect the relative positioning of the tank and workpiece wringing/support rolls.
An object of the present invention is to overcome the aforementioned drawbacks of the prior art. It is a further object of the present invention to provide a cost-effective shallow bath plastic pickling tank, including expandable seals which allow for thermal expansion of the trough and which further prevent the escape of pickling acid. A further object of the present invention is to provide a seal which prevents the escape of both pickling acid liquid and fumes through the seal.